Fluid actuated driving apparatus



Nov- 7, 19 7 P. A. READYHOUGH FLUID AGTUATED DRIVING APPARATUS 3 Sheets-Sheet 1 Filed Oct. 1965 7, 1967 P. A. READYHOUGH 3,351,256

FLUID ACTUATED DRIVING APPARATUS Filed Oct. 5, 1965 3 Sheets-Sheet 2 P. A. READYHOUGH Nov. 7, 1967 FLUID ACTUATED DRIVING APPARATUS 5 Sheets-Sheet 5 Filed Oct. 5. 1'565 United States Patent 3,351,256 FLUID ACTUATED DRIVING APPARATUS Peter A. Readyhough, Providence, R.I., assignor to Bost tch, incorporated, East Greenwich, R.I., a corporatron of Rhode Island Filed Oct. 5, 1965, Ser. No. 493,017 15 Claims. (Cl. 227-130) ABSTRACT OF THE DISCLOSURE valve by initially communicating air under pressure from the reservoir under the control of a trigger valve directly to the piston to start the movement of the driving piston away from the control valve, the continuation of the drive stroke being effected by reservoir pressure acting directly on the piston through the open end of the cylinder. The

control valve is normally biased into closed relation to the open end of the cylinder and is maintained out of such position by the cooperative engagement of the piston therewith. Actuation of the trigger valve changes the bias of the control valve through pressurization of a control chamber to maintain the control valve in its piston held position during the drive stroke of the piston. Deactuation of the trigger valve releases the changed pressure bias on the control valve permitting it to close the open end of the cylinder enabling the cylinder to be exhausted and the piston to be returned. The return movement of the piston is accomplished by air pressure acting on the diflerential pressure area of the piston. The final portion of the return movement of the piston moves the control valve out of engagement with the cylinder.

This invention relates to pneumatic driving apparatus and, more particularly, to heavy-duty pneumatic driving apparatus particularly adapted to drive fasteners into a workpiece. Pneumatically actuated driving tools are finding increasmg use as labor-saving devices which facilitate the performance of work. These tools are particularly useful as portable implements and as such may be utilized in a variety of environments in which they are frequently subected to adverse conditions such as extremes of temperature and/or contaminated atmospheres-under such circumstances, it is important that the tools operate reliably and without requiring excessive care in handling or substantial amounts of maintenance. It is an object of this invention to provide novel and improved pneumatic driving engines suitable for driving heavy-duty fasteners such as large nails.

Another object of the invention is to provide a novel and improved pneumatic driving engine that employs simplified valving.

Still another object of the invention is to provide a heavy-duty driving engine capable of driving a heavyduty fastener in a single stroke in an arrangement which I provides economical use of the pressure fluid employed.

Still another object of the invention is to provide a reliable portable pneumatic driving tool with a minimum number of moving components.

In accordance with the invention, there is provided a pneumatic driving engine which includes a cylinder having an open end, a pressure fluid reservoir, and a piston disposed in the cylinder for axial movement away from the open end in the driving stroke. The relationship of the piston and the cylinder is such that the piston may protrude from the open end of the cylinder. Disposed above the open end of the cylinder is a piston stop structure in the form of a shuttle having a first annular surface that engages the end of the piston to provide a first seal between the top of the piston and the reservoir and a second annular surface surrounding the first annular surface adapted to engage the end of the cylinder to provide a second seal, this of the main port between the cylinder and the reservoir. Also disposed in the housing for communication with the upper surface of the piston is an exhaust passage and the movable shuttle includes a seal component adapted to close the exhaust passage in a first shuttie position in which the second annular surface is spaced from the end of the cylinder so that the port between the reservoir and the cylinder is open. There is included control means for applying fluid pressure to the top of the piston when the shuttle is in said first position to move the piston away from the shuttle (breaking the seal at the first annular surface) and thus exposing the top of the piston to pressure from the reservoir through the main port to drive the piston rapidly in a powerful driving stroke. The shuttle is movable to a second position in which the exhaust passage is open and the main cylinder port is closed by engagement of the second annular surface with the open end of the cylinder to permit the piston to return toward the piston stop.

In the preferred embodiment, the fluid pressure applied to the top of the piston is applied through a control chamber that is normally at low pressure (open to atmosphere). Pressure applied to the control chamber acts to hold the shuttle in the first position to insure that the exhaust port is closed and continued build-up of pressure on the top of the piston moves the piston away from the shuttle breaking the first annular seal so that the piston is exposed to the full force of fluid pressure from the reservoir. The control chamber remains pressurized until the implement is to be reset, in response to motion of the piston, or release of an interlock actuated by the workpiece, or release of the manually operable trigger, for example. Release of the pressure in the control chamber allows the shuttle to move from the first position to the second position, closing the main cylinder-reservoir port and opening the exhaust port. As the top of the piston is then exposed to atmosphere through the open exhaust port, the piston may be returned to its normal or home position, preferably by fluid pressure. Upon return, the piston initially contacts the shuttle, making a seal at the first annular surface. After that seal has been made, the piston acts against the shuttle to move it from the second position to the first position to close the exhaust port and open the main cylinder-reservoir port but without leakage to the exhaust port, due to the completion of the piston-shuttle seal.

This structural arrangement provides a reliable heavyduty portable pneumatic driving engine suitable for use with apparatus for driving fasteners fed from a magazine to a workpiece. These fasteners may be heavy-duty fasteners such as large nails and the apparatus drives such fasteners in a single stroke. The apparatus includes only two moving parts (in addition to the simple control valve), the shuttle, and the piston. The shuttle includes a plurality of seals that cooperates with the housing (exhaust port) and the cylinder and piston and also forms a part of the control chamber. It is a reliable device particularly adapted for economical use as a portable implement over a wide range of environmental conditions.

Other objects, features and advantages of the invention will be seen as the following description of a particular embodiment thereof progresses, in conjunction with the drawings, in which:

FIGURE 1 is a side elevational view, with parts broken away, of a driving engine constructed in accordance with the invention employed in a fastener driving apparatus;

FIGURE 2 is a sectional view similar to FIGURE 1 showing the driving engine in fully actuated position;

FIGURE 3 is a sectional view of a portion of the driving engine showing the position of the components as the piston is returning;

FIGURE 4 diagrammatically illustrates a modified form of driving engine;

FIGURE 5 is a top view of the shuttle employed in the engine shown in FIGURE 4; and

FIGURES 6 and 7 are sectional views of the engine shown in FIGURE 4 showing two different stages of operation.

With reference to FIGURE 1, the implement includes a housing 10 to which is secured by suitable conventional means a magazine 12 suitable for holding a supply of fasteners to be driven and having in its forward end a nosepiece 14 which defines a drive track 16 into which the fastener is introduced from magazine 12 for driving by the engine disposed in housing 10.

That housing includes a handle portion 20 that defines a reservoir chamber 22 connected to a supply line 24. At the forward end of the handle portion 20 is a body portion 26 that defines a further reservoir chamber 28 in which is housed a cylinder sleeve 30. This cylinder sleeve is secured in the housing at its lower end and has a bumper 32 disposed therein at that point. The cylinder sleeve includes a lower cylindrical section 34 of a first diameter and an upper cylindrical section 36 of a second and larger diameter than lower section 34. Immediately above the transition between sections 34 and 36 are a plurality of ports 38 which communicate with reservoir chamber 28.

A piston structure 40 is housed within the cylinder sleeve 30. This piston structure has a lower piston member 42 that slides within the lower cylinder section 34 and an upper piston member 44 that slides within the upper cylinder section 36. Each of these piston members includes an O-ring or other suitable sealing means 46 that engages the cooperating portions of the interior wall of the cylinder sleeve 30. The upper piston member 44 includes a head portion 48 that extends above its main body portion and defines a flat annular upper surface 50.

The upper end of the housing body portion 26 is open and of a diameter greater than that of the cylinder sleeve 34. An annular flange 52 projects inwardly at a point above the open upper end of sleeve 30. A cap 54 is secured over the upper end of the housing and includes an exhaust port 56. In the center of cap 54 is a depending boss 58. Extending outwardly from the depending boss 58 is a horizontal surface 60 in which are disposed exhaust ports 62 which communicate through passageways 64 with exhaust passage 56. The cap and its depend ing boss 54 cooperate with flange 52 in the upper end of housing body 26 to define a chamber 66.

Disposed within that chamber is a shuttle 70 which functions as a combined piston stop and valve structure. This shuttle includes as its lower surface a resilient member 72 which functions as a seal member. Immediately above this surface on the inner side thereof there is a lip portion or flange 74 and extending upwardly from that flange is a cylindrical web 76 that has a plurality of passageways 78 extending through it. Above the vertical web is a horizontal outwardly extending web 80 that has secured on its upper surface a sealing member 82 that co-operates with the exhaust ports 62. Finally, at the outer periphery of the horizontal Web 80 is a vertical flange between the cap and the shuttle is a spring 100 which ap-,

plies, in the downward direction, a light biasing force on the shuttle 70.

The control chamber 66 is connected, by means of passage 102, to a chamber housing a valve lecve 104 which includes an exhaust port 106 and a supply .port 108. A

valve member 110 is positioned in the valve sleeve 104 t for movement between a first position in which the supply port 108 is closed when the exhaust port 106 is open (as shown in FIGURE 1) and a second position in which the supply port is open and the exhaust port is closed (as shown in FIGURE 2). This valve member 110 is connected by means of a valve rod 112 to a trigger 114. Reservoir air pressure normally biases the valve in the position shown in FIGURE 1, that is to open the exhaust port 106 and to close the supply port 108.

The position of the components of the driving engine when pressure is applied to the engine is indicated in FIGURE 1. In that condition, the piston 40 is in the upper part of the cylinder sleeve 30 (normal or home position). This is due to the pressure from the reservoir chambers acting through ports 38 on the under surface of the piston portion 44 which is larger than the upper surface of piston portion 42. Thus, the piston is urged upwardly and out of the cylinder sleeve 30 against the lower surface of the shuttle and its sealing member 72 to complete an annular seal between the surface 50 of the piston and an interior annular portion of the seal member 72. The force of the piston 40 against the shuttle moves the shuttle upward so that the seal 82 on the horizontal web of the shuttle closes the exhaust ports '62. This upward pressure of the piston 40 on the shuttle 70 exceeds the combined downward pressure applied to the shuttle from reservoir 28 through passage and the biasing force of spring 100. In this condition, the control chamber 66 is exhausted to atmosphere through the trigger valve sleeve 104.

When the trigger 114 is depressed, the valve member is moved upwardly to close exhaust port 106 and to open supply port 108 to pressurize the control chamber 66. The pressure in the control chamber acts on the shuttle itself to more firmly seat that shuttle against the exhaust ports 62. However, pressure also flows through the passages 78 in the vertical web 76 to act against the upper surface of piston 40. When the pressure on that upper surface is'sufiicient to overcome the differential applied to piston sections 42 and 44, the piston is moved downwardly away from the seal surface 72. As soon as that seal is broken, pressure from the reservoir is applied to the top of the piston through the large annular port between the open upper end of the cylinder sleeve 30 and the reservoir chamber 28. This large port allows the pressure fluid to act rapidly and directly against the piston 40 and drive it downwardly in a powerful fastener driving stroke so that the driver blade attached to the piston moves downwardly through the fastener drive track 16 and drives the fastener therein out of that drive track and into the workpiece in a single stroke.

The position of the components of the engine at this time is shown in FIGURE 2. In summary, the piston has been driven downwardly principally by pressure fluid acting through the large open port between the seal surface 72 and the end of cylinder sleeve 30. The shuttle is held in its upper position by pressure in the control chamber 66. When the tool is to be reset, as for example by release 75 of the trigger 114, the control valve element 110 moves to close supply port 108 and open exhaust port 106 so that pressure is exhausted from the control chamber 66. The release of this pressure allows the pressure from the reservoir 28 acting through passageway 90 together with the force of spring 100 to force the shuttle downward so that the outer portion of the seal surface 72 seats against the upper end of the cylinder 30 closing the port between the cylinder and the reservoir. This position is shown in FIGURE 3. In this position, the exhaust ports 62 are open to atmosphere so that the interior of the cylinder 30 above the piston 40 is exhausted to atmosphere. Under this condition, the pressure acting on the differential piston through ports 38 moves the piston upwardly to return it to the position shown in FIGURE 1. As the piston moves up to the top of the cylinder, it contacts the inner portion of seal member 72 creating an annular seal at that point and then moves the shuttle up first breaking the reservoir-cylinder seal and then seating the seal 82 against the exhaust ports 62 closing passages 64. The engine has then been reset and is ready for the next driving stroke.

It will be noted that the components of the driving engine are in the position shown in FIGURE 3 prior to application of pressure through line 24 to the implement. In other words, the spring 100 biases the shuttle 70 down to close the annular port between the reservoir 28 and cylinder sleeve 30 and to open the exhaust passages 60. Thus, on pressurizing the tool, the piston 40 will be driven upwardly to complete the seal between the shuttle 70 and the piston and only after that seal is completed, will the port between the cylinder 30 and the reservoir 28 be opened. Thus, there is provided protection against actuation of the piston 40 in a driving stroke merely due to application of pressure to the reservoir.

A number of modifications of this structure will be apparent to those skilled in the art. For example, the shuttlepiston and shuttle-cylinder seal surfaces on the shuttle 70 need not be in the same plane. Also, the reservoir-shuttle passage 90 may be omitted and spring 100 alone (typically somewhat heavier) acts to bias the shuttle downwardly. Alternatively, an arrangement as indicated in FIGURES 4-7 may be employed. That driving engine employs a four-way valve in place of the three-way valve structure employed in the apparatus shown in FIGURES 13. Two control chambers are provided for controlling the position of the shuttle and the pressure in these chambers is controlled by the four-way valve.

With reference to FIGURE 4, the engine includes a housing having a rearwardly extending handle portion 20' that defines a portion of a reservoir chamber 22'. At the forward end of the handle 20' is a body portion 26 that defines a further chamber 28' which functions as a reservoir and in which is disposed a cylinder sleeve 30 which houses a differential piston structure 40'. Secured at the upper end of the housing is a cap structure 54' which includes exhaust ports 56'. The cap carries a receptable 154 for receiving one end of biasing spring 100, and an annular exhaust passage seal element 156.

The shuttle 70 employed in this embodiment also functions as a combined piston stop-valve structure and includes on its lower surface a resilient member 72'. Extending upwardly from the lower surface is a cylindrical web 76 that has a plurality of radial passages 78' extending therethrough. Extending radially outwardly from an intermediate portion of the vertical web is a flange portion 160 that carries an O ring seal. The vertically extending web 76 terminates in an annular seal surface 164 which cooperates with the exhaust seal 156 carried by the cap. Extending inwardly from the lower portion of the shuttle from points adjacent resilient member 72' are four arms 170 which support a spring receiving member 172 in which the lower end of spring 100' is seated. It will be noted in the position of the shuttle 70' shown in FIGURE 4, a control chamber 150 is defined by the space below the flange portion 160 and a second control chamber 152 is defined by the space above the flange portion 160.

As indicated above, the control valve, which is actuated by a suitable trigger, is of the four-way type and includes a sleeve 180 disposed within a valve housing 182. Disposed within the sleeve is a valve actuator member 184 and a spring 186 biases the valve member 184 downwardly to the position shown in FIGURE-4. The valve housing 182 has an inlet port 190 connected to the reservoir 22; an exhaust port 192, a first control port 194 connected by means of passage 196 to control chamber 150 and a second control port 198 connected by means of passage 200 to control chamber 152.

When the driving engine is not pressurized, spring biases the shuttle 70 downwardly so that the seal member 72 contacts the upper end of cylinder 30 and closes that end. This provides protection against unintended driving of piston 40' upon pressurizing the tool. When pressure is applied to the tool, pressure flows through the ports 38' in cylinder 30 and acts against the differential piston to move it upwardly to first create an annular seal between the piston and the seal surface 72' and then break the seal between the shuttle and the cylinder, moving the components to the position shown in FIGURE 4. In this position, the four-way valve connects control port 194 to exhaust port 192 and control port 198 to pressurized inlet port 190 so that control chamber 152 is pressurized and con trol chamber is connected to atmosphere.

When the valve is actuated, control port 194 is connected to the reservoir and control port 198 is connected to atmosphere. This pressurizes control chamber 150 and pressurizes the space above the piston through shuttle ports 78. The pressure in control chamber 150 acts to hold the shuttle 70' in the position shown in FIGURE 4.

" As the pressure increases on the piston, it moves away from the shuttle, breaking the annular seal therebetween and full pressure from the reservoir is then imposed on the top of the piston 40 driving it downwardly rapidly in a powerful driving stroke. The positions of the components of the driving engine at this time are indicated in FIGURE 6.

To reset the engine, the control valve is returned to the position shown in FIGURE 4, pressurizing control chamber 152 and exhausting control chamber 150. The pressure in control chamber 152 acts on the flange and, together with the biasing force of spring 100', drives the shuttle 70' down to seat the sealing surfaces 72' on the upper end of the cylinder 30 and at the same time opens the exhaust ports 56'. As the portion of the cylinder above the piston thus evacuated opens to atmosphere, the pressure through cylinder ports 38' acting on the differential piston moves it upwardly towards the shuttle 70'. (The position of the engine components this time is indicated in FIG. 7.) When the piston contacts the shuttle seal surface 72, it provides a piston-shuttle seal at that point and then breaks the shuttle-cylinder seal and resets the components to the position indicated in FIG- URE 4.

Still other modifications will be apparent to those skilled in the art and, therefore, it is not intended that the invention be limited to the disclosed embodiments or to details thereof and departures therefrom may be made within the spirit and scope of the invention as defined in the claims.

What is claimed is:

1. A pneumatic driving tool comprising a cylinder having an end, a piston disposed in said cylinder for axial movement away from said open end in a driving stroke, a fastener driving element secured to said piston at one end thereof, a shuttle, means for supporting said shuttle adjacent said open end of said cylinder for movement between a first position and a second position, said shuttle including a first surface portion for engaging the piston surface opposed to said one end to provide a seal between said shuttle and said piston, means defining an exhaust passage having an orifice disposed for communication with said opposed surface of said piston, said piston being normally urged into sealing engagement with said first surface portion of said shuttle, a reservoir chamber for supplying fluid pressure to said cylinder through the open end thereof in a piston driving stroke, a port adjacent said open end of said cylinder providing communication between said reservoir and said cylinder, said piston when in position engaging said first surface portion blocking communication between said reservoir chamber and said cylinder through said port, said port being fully opened during the driving stroke of the piston away from said shuttle, and control means for applying pressure fluid to said opposed piston surface to move said piston away from said shuttle in a driving stroke, said supporting means and said shuttle defining a control chamber, said control means including means for applying pressure fluid to said control chamber to control the movement of said shuttle between said first and second positions, and means for normally urging said shuttle towards said cylinder for closing said port between said cylinder and said reservoir, said urging means defining a passage connected to said reservoir, and a valve in said passage between said reservoir and said shuttle.

2. A pneumatic fastener driving implement comprising a housing, a cylinder disposed in said housing having an open upper end and a lower end, a nosepiece structure defining a drive track for receiving fasteners from a magazine, means securing said nosepiece structure to said housing adjacent the lower end of said cylinder, a piston disposed in said cylinder for axial movement away from said upper end in a driving stroke, a fastener driving element secured to said piston at one end thereof for movement through said drive track during a driving stroke of said piston, a reservoir chamber in said housing for supplying fluid pressure to said cylinder through said open end thereof in a piston driving stroke, means defining an exhaust passage having an orifice disposed for communication with the surface of said piston opposed to said one end, a shuttle, means for supporting said shuttle adjacent said open end of said cylinder, said shuttle including a first surface portion for engaging the piston surface opposed to said one end to provide a seal between said shuttle and said piston and a second surface portion to close said exhaust passage, said piston being normally urged into sealing engagement with said first surface portion of said shuttle so that said second surface portion closes said exhaust passage, means defining a port adajcent said open end of said cylinder providing communication between said reservoir and said cylinder, said piston when in position engaging said first surface portion blocking communication between said reservoir chamber and said cylinder through said port, said port being fully opened during the driving stroke of the piston away from said shuttle, said shuttle including a third surface portion adapted to engage said cylinder to close said port, means for urging said shuttle towards said cylinder to cause said third surface portion to close said port and to cause said second surface portion to open said exhaust passage, and control means for applying pressure fluid to said opposed surface to move said piston away from said shuttle in a driving stroke while maintaining said second surface portion in closing relation relative to said exhaust passage, said supporting means and said shuttle defining a control chamber, said control means including means for applying pressure fluid to said control chamber to control the movement of said shuttle, said shuttle having a passage therein providing communication between said control chamber and said opposed surface of said piston.

3. The implement as claimed in claim 2 wherein said urging means includes a passage connected to said reservoir.

4. The implement as claimed in claim 2 wherein said supporting means and said shuttle further defines a second control chamber and wherein said control means 8 further includes means to control the application of fluid pressure to said second control chamber.

5. A pneumatic driving tool comprising a cylinder having an open end, a piston disposed in said cylinder for axial movement away from said open end in a driving stroke, a fastener driving element secured to said piston at one end thereof, a shuttle, means for supporting said shuttle adjacent said open end of said cylinder for movement between a first position and a second position, said shuttle including a first surface portion for engaging the piston surface opposed to said one end to provide a seal between said shuttle and said piston, means defining an exhaust passage having an orifice disposed for communication with said opposed surface of said piston, said piston being normally urged into sealing engagement with said first surface portion of said shuttle, a reservoir chamber for supplying fluid pressure to said cylinder through the open end thereof in a piston driving stroke, a port adjacent said open end of said cylinder providing communication between said reservoir and said cylinder, said piston when in position engaging said first surface portion blocking communication between said reservoir chamber and said cylinder through said port, said port being fully opened during the driving stroke of the piston away from said shuttle, and control means for applying pressure fluid to said opposed piston surface to move said piston away from said shuttle in a driving stroke, said supporting means and said shuttle defining a control chamber, said control means including means for applying pressure fluid to said control chamber to control the movement of said shuttle between said first and second positions, and means for normally urging said shuttle towards said cylinder for closing said port between said cylinder and said reservoir, said urging means including a spring.

6. A pneumatic driving tool comprising a cylinder having an open end, a piston disposed in said cylinder for axial movement away from said open end in a driving stroke, a fastener driving element secured to said piston at one end thereof, a shuttle, means for supporting said shuttle adjacent said open end of said cylinder for move ment between a first position and a second position, said shuttle including a first surface portion for engaging the piston surface opposed to said one end to provide a seal between said shuttle and said piston, means defining an exhaust passage having an orifice disposed for communication with said opposed surface of said piston, said piston being normally urged into sealing engagement with said first surface portion of said shuttle, a reservoir chamber for supplying fluid pressure to said cylinder through the open end thereof in a piston driving stroke, a port adjacent said open end of said cylinder providing communication between said reservoir and said cylinder, said piston when in position engaging said first surface portion blocking communication between said reservoir chamber and said cylinder through said port, said port being fully opened during the driving stroke of the piston away from said shuttle, and control means for applying pressure fluid to said opposed piston surface to move said piston away from said shuttle in a driving stroke, said supporting means and said shuttle defining a control chamber, said control means including means for applying pressure fluid to said control chamber to control the movement of said shuttle between said first and second positions, said shuttle having a passage therein providing communication between said control chamber and said opposed surface of said piston.

7. Fastener driving apparatus comprising housing :means defining:

a fluid pressure reservoir adapted to be communicated with a source of fluid under pressure, a cylindrical chamber having an open end disposed in communicating relation with said reservoir, an exhaust passage communicating with atmosphere,

and a drive track for receiving successive fasteners therein,

a piston mounted within said chamber for movement between first and second positions,

a fastener driving element operatively connected with said piston for movement through a drive stroke to drive a fastener received in said drive track outwardly thereof into a workpiece in response to the movement of said piston from said first position to said second position and for movement through a return stroke in response to the movement of said piston from said second position to said first position,

said piston having driving surface means facing generally in a direction opposed to the direction of movement of said piston toward said second position including an outer annular portion disposed in outwardly spaced relation to the open end of said chamber when said piston is disposed in said first position,

control valve means mounted for movement between a first position disposed in outwardly spaced relation to the open end of said chamber and a second position disposed in sealing engagement with the open end of said chamber,

actuating means movable between a normal inoperative position and an operative position,

said control valve means including an annular portion disposed in a position to be engaged by the outer annular portion of said piston driving surface, means during the movement thereof outwardly of the open end of said chamber and providing an annular seal therewith when said control valve means and said piston are disposed in said first positions to thereby prevent communication of air under pressure in said reservoir with the interior of said chamber and the driving surface means of said piston interiorly of the outer annular portion thereof,

said control valve means being biased toward said second position when said actuating means is disposed in said normal inoperative position,

said piston being biased toward said first position when said actuating means is disposed in said normal inoperative position with a force sufficient to overcome the bias of said control valve means and thereby maintain the latter in said first position,

means operable in response to the movement of said actuating means into said operative position for introducing air under pressure from said reservoir into communication with said piston driving surface means interiorly of the sealing engagement of said control valve means with the outer annular portion thereof sufi'icient to overcome the bias of said piston toward said first position and to initiate the movement of said piston away from said first position and for changing the bias of said control valve means to a direction toward the first position thereof so that said control valve :means will remain in said first position during the initial movement of said piston away from its first position permitting air under pressure from the reservoir to pass between said control valve means and the open end of said chamber into the latter to act on the driving surface means of the piston and effect a rapid movement of the latter into its second position, and

means for preventing communication between said piston driving surface means and said exhaust passage during the movement of said piston from said first position to said second position and for communicating said piston driving surface means with said exhaust passage during the movement of said piston from said second position to said first position.

8. Apparatus as defined in claim 7 wherein said means operable in response to the movement of said actuating means comprises means defining a control chamber and wherein said actuating means includes a valve mechanism operatively connected between said reservoir and said control chamber for introducing air under pressure 10 from said reservoir to said control chamber in response to the movement of said actuating means into said operating position and for exhausting air under pressure in said control chamber in response to the movement of said actuating means into said inoperative position,

said control chamber defining means including a portion of said control valve means against which air under pressure within said control chamber acts to bias said control valve means in a direction toward the first position thereof.

9. Apparatus as defined in claim 8 wherein said means operable in response to the movement of said actuating means further includes a restricted passage in the portion of said control valve means defining said control chamber communicating at one end thereof with said control chamber and at the other end thereof with the driving surface means of said piston interiorly of said outer annular portion thereof.

10. Apparatus as defined in claim 9 wherein said control valve means includes a shuttle member having an annular portion forming a part of the control chamber defining portion of said control valve means,

said restricted passage extending through said annular shuttle member portion,

said annular shuttle member portion having a cylindrical exterior surface, said housing means further defining an opening receiving said annular shuttle member portion, and

annular sealing means between said opening and the cylindrical exterior surface of said shuttle member portion. 11. Apparatus as defined in claim 8 wherein said control valve means is biased toward said second position by spring means acting between said housing means and said control valve means and wherein said valve mechanism comprises a three way valve mechanism. 12. Apparatus as defined in claim 8 wherein said means operable in response to the movement of said actuating means further includes means defining a second control chamber and wherein said valve mechanism comprises a four way valve mechanism operable to exhaust air under pressure in said second control chamber in response to the movement of said actuating means into said operative position and to communicate air under pressure from said reservoir to said control chamber in response to the movement of said actuating means into said inoperative position,

said second control chamber defining means including a portion of said control valve means against which air under pressure within said second control chamber acts to bias said control valve means in a direction toward the second position thereof.

13. Apparatus as defined in claim 7 wherein said last mentioned means comprises cooperating annular sealing portions on said control valve means and said housing means arranged to be in sealing engagement when said control valve means is in the first position thereof and to be in spaced relation with respect to each other when said control valve means is in the second position thereof,

said control valve means including an opening an ranged to communicate with the interior of said cylinder when said control valve means is in the second position thereof,

said cooperating annular sealing portions being disposed between said opening and said exhaust passage.

14. Apparatus as defined in claim 7 wherein said housing means further defines a second cylindrical chamber of a diameter size less than the diameter size of said first mentioned cylindrical chamber,

said second chamber being axially aligned with said first mentioned chamber and communicating with the end of the latter opposite from the open end thereof,

said piston including first and second axially spaced annular sealing means slidably sealing engaging said first mentioned and second chambers respectively and an exterior configuration between said first and second annular sealing means defining a differential pressure surface area facing in a direction opposed to the driving surface means of said piston, and

means for introducing and maintaining air pressure from said reservoir within the communicating ends of said chambers acting on said differential pressure surface area to bias said piston in a direction toward the first position thereof.

12 15. Apparatus as defined in claim 14 wherein said last mentioned means comprises an opening com municating the end of said first mentioned chamber adjacent said second chamber with said reservoir at all times.

References Cited UNITED STATES PATENTS 3,027,875 4/1962 Spencer -a 914l7 10 3,043,272 7/1962 Wandel.

3,200,716 8/1965 Le Sage 91417 MARTIN P. SCHWADRON, Primary Examiner.

15 PAUL E. MASLOUSKY, Examiner. 

1. A PNEUMATIC DRIVING TOOL COMPRISING A CYLINDER HAVING AN END, A PISTON DISPOSED IN SAID CYLINDRICAL FOR AXIAL MOVEMENT AWAY FROM SAID OPEN END IN A DRIVING STROKE, A FASTENER DRIVING ELEMENT SECURED TO SAID PISTON AT ONE END THEREOF, A SHUTTLE, MEANS FOR SUPPORTING SAID SHUTTLE ADJACENT SAID OPEN END OF SAID CYLINDER FOR MOVEMENT BETWEEN A FIRST POSITION AND A SECOND POSITION, SAID SHUTTLE INCLUDING A FIRST SURFACE PORTION FOR ENGAGING THE PISTON SURFACE OPPOSED TO SAID ONE END TO PROVIDE A SEAL BETWEEN SAID SHUTTLE AND SAID PISTON, MEANS DEFINING AN EXHAUST PASSAGE HAVING AN ORIFICE DISPOSED FOR COMMUNICATION WITH SAID OPPOSED SURFACE OF SAID PISTON, SAID PISTON BEING NORMALLY URGED INTO SEALING ENGAGEMENT WITH SAID FIRST SURFACE PORTION OF SAID SHUTTLE, A RESERVOIR CHAMBER FOR SUPPLYING FLUID PRESSURE TO SAID CYLINDER THROUGH THE OPEN END THEREOF IN A PISTON DRIVING STROKE, A PORT ADJACENT SAID OPEN END OF SAID CYLINDER PROVIDING COMMUNICATION BETWEEN SAID RESERVOIR AND SAID CYLINDER, SAID PISTON WHEN IN POSITION ENGAGING SAID FIRST SURFACE PORTION BLOCKING COMMUNICATION BETWEEN SAID RESERVOIR CHAMBER AND SAID CYLINDER THROUGH SAID PORT, SAID PORT BEING FULLY OPENED DURING THE DRIVING STROKE OF THE PISTON AWAY FROM SAID SHUTTLE, AND CONTROL MEANS FOR APPLYING PRESSURE FLUID TO SAID OPPOSED PISTION SURFACE TO MOVE SAID PISTON AWAY FROM SAID SHUTTLE IN A DRIVING STROKE, SAID SUPPORTING MEANS AND SAID SHUTTLE DEFINING A CONTROL CHAMBER, SAID CONTROL MEANS INCLUDING MEANS FOR APPLYING PRESSURE FLUID TO SAID CONTROL CHAMBER TO CONTROL THE MOVEMENT OF SAID SHUTTLE BETWEEN SAID FIRST AND SECOND POSITIONS, AND MEANS FOR NORMALLY URGING SAID SHUTTLE TOWARDS SAID CYLINDER FOR CLOSING SAID PORT BETWEEN SAID CYLINDER AND SAID RESERVOIR, AND URGING MEANS DEFINING A PASSAGE CONNECTED TO SAID RESERVOIR, AND A VALVE IN SAID PASSAGE CONNECTED TO RESERVOIR AND SAID SHUTTLE. 